Graph description: How do I compare methods of measurement which give results in different units?, 2

The figure shows a plot of FEV against PEF: FEV on the vertical axis, PEf on the horizontal axis. Each point from the table is plotted as a circle and there is a positive relationship. Subjects with high PEF tend to have high FEV.

The regression line, the line of best fit, is shown. It has a positive gradient.

The prediction interval is included. This is the distance between are two curved lines, one above the regression line and the other below. Both are closest to the regression line near the middle and get further away at each end.

Back to Sample size for a study of agreement between two methods of measurement.

This page maintained by Martin Bland.
Last updated: 12 January, 2004.